Registers – Coded record sensors – Particular sensor structure
Patent
1993-05-07
1995-10-31
Hajec, Donald
Registers
Coded record sensors
Particular sensor structure
G06K 710
Patent
active
054632110
ABSTRACT:
A method and apparatus for determining the transitions between binary levels of an input signal such as a scanned bar code label by detecting zero crossings of an approximated second derivative of the input signal. Samples of the input signal are obtained by using delay lines, sample-and-hold circuits, an analog shift register or similar device. The first derivative of the signal is approximated by the slope of a straight line between two sampled points on the waveform. The second derivative is approximated by the difference between two first derivatives. Zero crossings of the second derivative indicating transitions of the input signal may be determined either by detecting a signal peak on both sides of the zero crossing, or by comparing the second derivative signal to zero when the first derivative exceeds a positive or negative threshold. The time between sample points may be adjusted to match a particular range setting of a scanner having a plurality of range settings.
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Arends Thomas C.
Elliott Randy D.
Filipek Jeffrey R.
Hajec Donald
Spectra-Physics Scanning Systems, Inc.
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